Epidemiology of Staphylococcus aureus bacteremia in Denmark from 1957 to 1990.

OBJECTIVE: To investigate the changes in epidemiology of Staphylococcus aureus (SA) bacteremia in Denmark over a 30-year period, where the population has remained stable. METHODS: Bacteriologic and clinical data were generated on 17 712 SA strains from virtually all SA bacteremia cases in Denmark from 1957 to 1990 submitted to our laboratory for phage typing. The data were related to information about population, hospital activity and blood-culturing activity during that period. RESULTS: SA bacteremia cases increased from 3 to 20/100 000 inhabitants per year, with the largest increases in incidence rates for the <1-year and >50-year age groups. While blood-culturing activity increased three-fold during the period, the rate of SA bacteremias actually decreased relative to the number of blood cultures taken. The increase in SA bacteremia cases was mainly due to increases in nosocomial infections for all age groups and was related to the increasing admission rates to Danish hospitals. Major shifts in antibiotic resistance patterns and phage types took place during the period, i.e. a marked reduction in multiresistant (including methicillin-resistant) strains, but could not explain the change in the epidemiology of the infections. CONCLUSIONS: The data indicate that increases in SA bacteremia rates correlated significantly with increasing numbers of admissions to hospitals. The main increase in SA bacteremia rates was represented by nosocomial infection, although increasing blood-culturing activity during the period may have contributed.